The invention relates to a valve arrangement for regulating the idling speed of internal combustion engines by controlling the quantity of air on the intake side of an intake manifold leading to the internal combustion engine, having an electromechanical control member which has a solenoid by which a closure member can be moved via a control element against the force of a return spring.
Such valve arrangements serve to keep the idling rpm of the engine as low as possible but at the same time also regulate it in such a manner that, in case of additional loads such as result, for instance, from auxiliary units in a vehicle, the idling speed does not drop down to such a point that the engine stalls. For this purpose, the solenoid is acted on by a control current which is formed, inter alia, as a function of the actual rpm and which effects such a displacement of the closure member that the actual speed reaches a predetermined desired speed substantially independently of disturbing variables.
When the solenoid is without current, the control member and, together with it, the closure member are moved by the return spring into either the fully open or the fully closed position. This occurs when no current acts on the solenoid aside from the automotive operation. However, this may also take place as a result of a defect by which the current supply to the solenoid is interrupted.
In the traditional valve arrangements this has the result that the engine operates either with a maximum idling speed or with a minimum idling speed with the danger of stalling.
The object of the invention is, therefore, to create a valve arrangement of the type described above which, by simple means, assures an idling speed which is as low as possible but at all times sufficiently high to prevent stalling of the engine in the event of a failure of the solenoid.